What is its speed at point A? Answer in units of m/s. } DID If electricity costs

Question

What is its speed at point A? Answer in units of m/s. } DID If electricity costs 20 cen it cost to run the compre Answer in units of cents Question 12, chap 108, sect 5. part 1 of 2 10 points Lora (72 kg) is an expert skier. If she starts at 4.5 m/s at the top of the lynx run, which is 100 m above the bottom, What is her final kinetic energy at the bot- tom of the ski run? Answer in units of J. Question 13, chap 108, sect 5. part 2 of 2 10 points What is her speed at the bottom? Answer in units of m/s.

Explanation / Answer

Given,

m = 72 kg ; h = 100 m ; v = 4.5 m/s

a)from the conservation of energy

Ef = Ei

Ei = KE + PE

Ei = 1/2 m vi^2 + m g h

Ei = 0.5 x 72 x 4.5^2 + 72 x 9.8 x 100 = 71289 J

at the bottom of the hill all the energy she has is kinetic energy only

KE(final) = 71289 J

b)we have, KE(final) = 71289

1/2 m vf^2 = 71289

vf = sqrt (2 x 71289/72) = 44.5 m/s

Hence, vf = 44.5 m/s

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